Electron discharge tube



Aug. 22, 1939; B D N 2,170,410

ELECTRON DISCHARGE TUBE Original Filed March 29, 1937 IN ENTOR v r ye RNEY Patented Aug. 22, 1939 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE TUBE- George J; Imboden, Emporium, Pa., assignor to Hygrade Sylvania Corporation," Salem; Mas's., a corporation of Massachusetts 1 Original application March 29, 1937, Serial No. 133,541. Divided and this application April 2,

1938, Serial No. 199,550

1 Claim. (Cl. 250 -275) This invention relates to electron discharge tubes and more particularly to such tubes as employ electron emitters of the indirectly heated or unipotential type.

5 A principal object of the invention is to provide an improved structure of indirectly heated cathode for radio'tubes and the like.

A feature of the invention relates to an indirectly heated cathode which is specially shaped 10 to prevent it slipping, turning or changing its spacial relation with respect to the remaining electrodes of a tube mount.

A further feature relates to a specially shaped cathode sleeve for an indirectly heated cathode 15 having a connector tab fastened thereto in such a position as to avoid the necessity of employing a notched circular perforation in the usual mica or ceramic insulator spacer.

Other features and advantages not specifically 20 enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

While the invention will be illustrated herein as embodied in an electron discharge tube of 25 the triode type, it will be understood that this is done merely for explanatory purposes and not by way of limitation. Accordingly in the drawing:

Fig. 1 is a vertical elevational view, partly in 30 section, of a typical radio tube mount embodying the invention.

Fig. 2 is a top plan view of the mount of Fig. 1.

Fig. 3 is an enlarged plan view of part of Fig. 2.

35 Fig. 4 is another enlarged plan view of certain parts, of Fig. 2.

Fig. 5 is an enlarged elevational View of certain parts of Fig. 1.

Fig. 6 is a side view of Fig. 5.

40 Referring to Fig. 1, the numeral I rep-resents in dotted outline any well known form of enclosing envelope such as customarily employed in radio tubes and the like and while the drawing shows an envelope of the glass type, it will 45 be understood that a metal envelope may be employed. Sealed into the envelope is any well known form of radio tube mount comprising the stem or base 2 wherein are sealed the various lead-in and support wires 5 to II inclusive.

50 Supported on the wires 5 and II is the anode [2, preferably, although not necessarily, in the form of a flattened tubular member of metal, graphite, carbon or the like. Supported on the wires 6 and I is the grid electrode l3 which 55 may be of any well known foraminous structure and merely for purposes of illustration it is shown in the drawing in the form of a fine helically wound wire supported on and attached to" the grid siderods l4, l5.

Coaxially disposed within both the grid and plate is an indirectly heated cathode according to the invention which cathode is indicated generally by the numeral l6. Supported within the cathode and suitably insulated therefrom is any well known form of heater wire the free ends of which are connected to the wires 7 and 9. For the purpose of making electrical connection to the emissive coating on the cathode there is provided a metal tab I 1 which is connected to the wire 8. In order to maintain the spacial positions of the various electrodes there are provided upper and lower insulator spacer members l8 and I9 respectively, these members being of any suitable insulation material. Preferably, although not necessarily, members l8 and I9 are of mica sheets or discs having the necessary perforations to receive the ends of the various side rods and also the ends. of the cathode, it being understood that the mica discs are held in place on the wires 5 and l I by metal tabs, eyelets or similar means fastened to the said wires.

In accordance with the invention, the cathode comprises a metal sleeve of nickel or other similar metal having a flattened tubular portion 20 at its upper end and a similar flattened tubular portion 2| at its lower end. The intervening or main body portion 22 is cylindrical and is provided with a coating 23 of any well known electron emissive material. The flattening of the ends of the sleeve results in the forming of upper and lower shoulders 24, 25, which are adapted to engage the mica spacer members l8, 19 respectively so that the cathode sleeve can be held firmly between the micas and is prevented from shifting or sliding vertically. Each of the mica members is provided with an elongated perforation 26 as shown in enlarged form in'Fig. 4.. Each perforation has substantially the same boundary shape as the cross-sectional shape of the flattened ends 20, 2| and preferably the ends 20, 2| are closely fitted within the perforations 26 allowing for the usual clearance tolerances ordinarily employed in devices of this character. As indicated in Figs.

5 and 6, the cathode tab 11 is disposed within the flattened end 2! to which it may be welded, consequently both the upper and lower spacers l8, l9, can be perforated in an identical manner. I-Ieretofore, it has been the usual practice to weld the tab IT to the outer face of the cathode sleeve, thus necessitating the provision of a circular per- 2 foration in the lower mica the edge of the perforation requiring a notch to accommodate the tab. This notching not only increased the cost of fabricating the mica but also required two separate kinds of micas, namely those for the tops of mounts and those for the bottoms of mounts.

By reason of the flattened tubular ends 20, 2|

and the correspondingly shaped perforations 26,

relative turning of the cathode sleeve is positively prevented, consequently the sleeve is positively locked against vertical sliding movement and turning movement about its vertical axis.

The particular shape of cathode shown, reduces the cost of manufacture of the tube and also reduces the percent of rejects. This results from the fact that the assembly or threading of the micas on to the sleeve merely requires the insertion of the ends 20, 2|, into the perforations 26 which automatically determines the positioning of the sleeve, and the shoulders 24, 25, positively prevent the micas coming in contact with the emissive coating. Furthermore, the shoulders 24, 25, positively space the micas from the end turns of the grid and serve as means for accurately spacing the mica members vertically apart.

that the flattened tubular portions may be provided at either or both ends of the cathode. This application is a division of application Serial No.

' 133,541, filed March 29, 1937.

What I claim is:

A radio tube mount comprising an indirectly heated cathode, a surrounding electrode for said cathode said electrode having at least one side rod projecting beyond the ends thereof, a pair of insulator spacer members having aligned openings to receive the ends of said cathode and said side rod, said cathode having a cylindrical body portion terminating in flattened tubular ends the junctures between the ends and body portion defining shoulders, each of said spacer members having a perforation substantially the same as the peripheral cross-section of said end portions whereby said cathode is positively locked against turning, and means for fastening said spacer members on said side rod so that they abut against said shoulders at opposite ends of said cathode.

GEORGE J. IMBODEN. 

